A radiant heater for an electric cooker comprises in general a base layer of thermal insulation material typically having an upstanding peripheral wall, and a heating element in the form of a coil or bare resistance wire secured to the base layer of thermal insulation material.
It is known to secure the heating element in position on the base layer by means of staples and by means of refractory glue. However, although staples are effective where the base layer is a compacted particulate material capable of exerting sufficient frictional force to prevent easy withdrawal of the staples, staples are not sufficiently firmly held where the base layer is a fibrous material. In addition, the use of staples renders difficult any automation of the securing of the heating element to the base layer because it is necessary to apply a stapling gun between adjacent turns of the heating element so as to avoid crushing the heating element and to locate accurately that portion of the heating element which bears on the base layer. In practice, the pitch of the turns of the heating element varies along its length which makes it impossible to predict the precise location of the turns for applying the stapling gun between the turns without human assistance.
On the other hand, the use of a refractory glue is effective where the base layer is a fibrous material and also facilitates automation of the securing of the heating element because glue can be applied accurately to the base layer. However, refractory glues when used with base layers in the form of compacted particulate material can interfere with the cohesive strength of the material and so lead to an unreliable joint between the heating element and the base layer.
It is an object of the present invention to provide a radiant heater for an electric appliance in which a heating element can be secured to a base layer of compacted particulate material by means of an adhesive material such as glue.